1. Technical Field
The present invention relates to an ink composition and a recording method.
2. Related Art
In recent years, techniques for forming images using photocurable ink compositions curable with light such as ultraviolet light have been widely used for printing by ink jet recording. The use of such photocurable ink compositions allows images having high color developability and weather resistance to be formed on, for example, recording media having low ink absorbency.
A photocurable ink composition usually contains a colorant, a polyfunctional monomer, and an ultraviolet polymerization initiator at least and is designed to exhibit desired performance by controlling the type, content, and/or combination of these compounds.
Methods for ejecting ink compositions from ink jet recording heads to apply the ink compositions to recording media need to be capable of forming fine images. Therefore, for example, attempts have been made to increase the density of nozzles for ejecting ink and to reduce the volume of droplets of ejected ink compositions as disclosed in JP-A-2008-179076.
Photocurable ink compositions contain high-viscosity compounds or high-molecular weight compounds, such as polymers or oligomers, for increasing the performance of the photocurable ink compositions in some cases. When the photocurable ink compositions contain such compounds, heads for ejecting the photocurable ink compositions need to have increased discharge capacity.
In the development of such ink compositions, the type and/or amount of components contained in the ink compositions is limited depending on, for example, head capacity. Even if heads have a discharge capacity sufficiently large with respect to the type and amount of desired components, the heads fail to form ink droplets in some cases. For example, when an ink composition is ejected from nozzles, droplets of the ink composition are unlikely to fly separately or fine droplets (satellites) other than desired droplets are formed in some cases. This leads to a reduction in quality of an image to be recorded.
The inventors have made investigations on the basis of the idea that a cause of such a failure is the dynamic change in shape of an ink composition near a nozzle. As a result, the inventors have found that droplets of the ink composition can be stably ejected from the nozzle so as to have a uniform shape as designed in such a manner that the expansibility of the ink composition is controlled within a specific range.